Compositions and methods for thermosetting molecules in organic compositions

ABSTRACT

In a method of producing a low dielectric constant polymer, a thermosetting monomer is provided, wherein the thermosetting monomer has a cage compound or aryl core structure, and a plurality of arms that are covalently bound to the cage compound or core structure. In a subsequent step, the thermosetting monomer is incorporated into a polymer to form the low dielectric constant polymer, wherein the incorporation into the polymer comprises a chemical reaction of a triple bond that is located in at least one of the arms. Contemplated cage compounds and core structures include adamantane, diamantane, silicon, a phenyl group and a sexiphenylene group, while preferred arms include an arylene, a branched arylene, and an arylene ether. The thermosetting monomers may advantageously be employed to produce low-k dielectric material in electronic devices, and the dielectric constant of the polymer can be controlled by varying the overall length of the arms.

FIELD OF THE INVENTION

[0001] The field of the invention is reduction of dielectric constants.

BACKGROUND OF THE INVENTION

[0002] As interconnectivity in integrated circuits increases and thesize of functional elements de-creases, the dielectric constant ofinsulator materials embedding the metallic conductor lines in integratedcircuits becomes an increasingly important factor influencing theperformance of the integrated circuit. Insulator materials having lowdielectric constants (i.e., below 3.0) are especially desirable, becausethey typically allow faster signal propagation, reduce capacitiveeffects and cross talk between conductor lines, and lower voltages todrive integrated circuits.

[0003] Since air has a dielectric constant of about 1.0, a major goal isto reduce the dielectric constant of insulator materials down towards atheoretical limit of 1, and several methods are known in the art forincluding air into the insulator materials to reduce the dielectricconstant of such materials. In some methods, air is introduced into theinsulator material by generating nanosized voids in a compositioncomprising an adequately crosslinked thermostable matrix and athermolabile (thermally decomposable) portion, which is eitherseparately added to the thermostable matrix material (physical blendingapproach), or built-in into the matrix material (chemical graftingapproach). In general, the matrix material is first crosslinked at afirst temperature to obtain a three-dimensional matrix, then thetemperature is raised to a second, higher temperature to thermolyze thethermolabile portion, and cured at a third, still higher temperature toanneal and stabilize the desired nanoporous material that has voidscorresponding in size and position to the size and position of thethermolabile portion.

[0004] In both the physical blending approach and the chemical graftingapproach, nanoporous materials with desirable dielectric constants ofabout 2.5 and below may be achieved. However, while there is typicallyonly poor control over pore size and pore distribution in the physicalblending approach, the chemical grafting approach frequently posessignificant challenges in the synthesis of the polymers and prepolymersand inclusion of various reactive groups (e.g., to enable crosslinking,addition of thermolabile groups, etc.) into the polymers andprepolymers. Moreover, the chemical nature of both the thermolabileportion and thermostable matrix generally limits processing temperaturesto relatively narrow windows which must distinguish the crosslinking(cure) temperature, thermolysis temperature and glass transitiontemperature, thereby significantly limiting the choice of availablematerials.

[0005] In other methods, air or other gas (i.e. voids) is introducedinto the insulator material by incorporation of hollow, nanosizedspheres in the matrix material, whereby the nanosized spheres acts as a“void carriers”, which may or may not be removed from the matrixmaterial. For example, in U.S. Pat. No. 5,458,709 to Kamezaki et al.,the inventors teach the use of hollow glass spheres in an insulatormaterial. However, the distribution of the glass spheres is typicallydifficult to control, and with increasing concentration of the glassspheres, the dielectric material loses flexibility and other desirablephysico-chemical properties. Furthermore, glass spheres are generallylarger than 20 nm, and are therefore not suitable for nanoporousmaterials where pores smaller than 2 nm are desired.

[0006] To produce pores with a size substantially smaller than glassspheres, Rostoker et al. describe in U.S. Pat. No. 5,744,399 the use offullerenes as void carriers. Fullerenes are a form of carbon containingfrom 32 atoms to about 960 atoms, which are believed to have thestructure of a spherical geodesic dome, many of which are believed tooccur naturally. The inventors mix a matrix material with fullerenes,and cure the mixture to fabricate a nanoporous dielectric, wherein thefullerenes may be removed from the cured matrix. Although the poresobtained in this manner are generally very uniform in size, homogeneousdistribution of the void carriers still remains problematic. Moreover,both Rostoker's and Kamezaki's methods require addition or admixture ofthe void carriers to a polymeric material, thereby adding essentialprocessing steps and cost in the fabrication of nanoporous materials.

[0007] Although various methods are known in the art to introducenanosized voids into low dielectric constant material, all, or almostall of them have disadvantages. Thus, there is still a need to provideimproved compositions and methods to introduce nanosized voids indielectric material.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a method of producing a lowdielectric constant polymer. In one step, a star-shaped thermosettingmonomer having a core structure and a plurality of arms is provided, andin a subsequent step the thermosetting monomer is incorporated into apolymer, wherein the incorporation into the polymer comprises a reactionof a triple bond that is located in at least one arm.

[0009] In one aspect of the inventive subject matter, the core structureis a cage compound or aryl, and preferred arms are aryl, branched arylor arylene ether. It is also preferred that where the core structure isa cage compound, at least one of the arms has a triple bond. Where thecore structure is an aryl compound, it is preferred that all of the armshave a triple bond. Especially contemplated core structures includeadamantane, diamantane, a phenyl, and a sexiphenylene, and especiallycontemplated arms include a tolanyl, a phenylethynylphenylethynylphenyl,a p-tolanylphenyl, a 1,2-bis(phenylethynyl)phenyl, and a p-tolanylphenylether.

[0010] In another aspect of the inventive subject matter, theincorporation of the thermosetting monomer includes a reaction on morethan one triple bond, preferably on three triple bonds located on threearms, and more preferably on all triple bonds located in all arms. Inparticularly preferred aspects of the inventive subject matter, theincorporation takes place without participation of an additionalmolecule and preferably comprises a cyclo-addition reaction.

[0011] While it is generally contemplated that the thermosetting monomeris incorporated in a back-bone of a polymer, other positions includingthe termini and side chains are also appropriate. Preferred polymersinclude poly(arylene ethers) and polymers comprising, or consisting ofcontemplated thermosetting monomers. It is especially contemplated thatby increasing the length of the arms of the thermosetting monomers, themonomers will define an increased void volume between the monomers aftercrosslinking, thereby decreasing the density of the crosslinkedstructure and decreasing the dielectric constant of the polymer.

[0012] Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0013] FIGS. 1A-1C are exemplary structures for star shapedthermosetting monomers having an adamantane, a diamantane, and a siliconatom as a cage compound, respectively.

[0014] FIGS. 2A-2B are exemplary structures for star shapedthermosetting monomers having a sexiphenylene as an aryl group.

[0015] FIGS. 3A-3C are exemplary synthetic schemes for star shapedthermosetting monomers according to the inventive subject matter.

[0016]FIG. 4 is an exemplary scheme for the synthesis of substitutedadamantanes with aryl arms of varying length.

DETAILED DESCRIPTION

[0017] As used herein, the term “low dielectric constant polymer” refersto an organic, organometallic, or inorganic polymer with a dielectricconstant of approximately 3.0, or lower. As also used herein, the term“cage compound” refers to a molecule in which a plurality of ringsformed by covalently bound atoms define a volume, such that a pointlocated within the volume can not leave the volume without passingthrough a ring. For example, adamantane-type structures, includingadamantane and diamantane are considered a cage compound. In contrast,ring compounds with a single bridge such as norbornane(bicyclo[2.2.1]heptane) are not considered a cage compound, because therings in a single bridged ring compound do not define a volume.

[0018] In a method of producing a low dielectric constant polymer, athermosetting monomer is provided having a general structure as shown inStructure 1,

[0019] wherein Y is selected from a cage compound and a silicon atom,and R₁, R₂, R₃, and R₄ are independently selected from an aryl, abranched aryl, and an arylene ether, and wherein at least one of thearyl, the branched aryl, and the arylene ether has a triple bond. In afurther step, the thermosetting monomer is incorporated into a polymerthereby forming the low dielectric constant polymer, wherein theincorporation into the polymer comprises a chemical reaction of the atleast one triple bond. As used herein, the term “aryl” without furtherspecification means aryl of any type, which may include, for example abranched aryl, or an arylene ether. Exemplary structures ofthermosetting monomers that include an adamantane, a diamantane, and asilicon atom are shown in FIGS. 1A, 1B, and 1C, respectively, wherein nis an integer between zero and five, or more.

[0020] In another method of producing a low dielectric constant polymer,a thermosetting monomer is provided having a general structure as shownin Structure 2,

[0021] wherein Ar is an aryl, and R′₁-R′₆ are independently selectedfrom an aryl, a branched aryl, an arylene ether arid nothing, andwherein each of the aryl, the branched aryl, and the arylene ether haveat least one triple bond. In a subsequent step, the thermosettingmonomer is incorporated into a polymer thereby forming a low dielectricconstant polymer, wherein the incorporation into the polymer comprises achemical reaction of the at least one triple bond. Exemplary structuresof thermosetting monomers that include a tetra-, and a hexasubstitutedsexiphenylene are shown in FIGS. 2A and 2B, respectively.

[0022] Thermosetting monomers as generally shown in Structures 1 and 2may be provided by various synthetic routes, and exemplary syntheticstrategies for Structures 1 and 2 are shown in FIGS. 3A-3C. FIG. 3Adepicts a preferred synthetic route for the generation of star shapedthermosetting monomers with an adamantane as a cage compound, in which abromoarene is phenylethynylated in a palladium catalyzed Heck reaction.First, adamantane (1) is brominated to tetrabromoadamantane (TBA) (2)following a procedure previously described (J. Org. Chem. 45, 5405-5408(1980) by Sollot, G. P. and Gilbert, E. E.). TBA is reacted with phenylbromide to yield tetrabromophenyladamantane (TBPA) (4) as described inMacromolecules, 27, 7015-7022 (1990) by Reichert, V. R, and Mathias L.J., and TBPA is subsequently reacted with a substituted ethynylaryl in apalladium catalyzed Heck reaction following standard reaction proceduresto yield tetraarylethynylphenyladamantane (TAEPA) (5). Thepalladium-catalyzed Heck reaction may also be employed for the synthesisof a star shaped thermosetting monomer with a sexiphenylene as thearomatic portion as shown in FIG. 2C and FIG. 2D, in which atetrabromosexiphenylene and a hexabromosexiphenylene, respectively, isreacted with an ethynylaryl to yield the desired corresponding starshaped thermosetting monomer.

[0023] Alternatively, TBA (supra) can be converted to a hydroxyarylatedadamantane, which is subsequently transformed into a star shapedthermosetting monomer in a nucleophilic aromatic substitution reaction.In FIG. 3B, TBA (2) is generated from adamantane (1) as previouslydescribed, and further reacted in an electrophilic tetrasubstitutionwith phenol to yield tetrakis(hydroxyphenyl) adamantane (THPA) (7).Alternatively, TBA can also be reacted with anisole to givetetrakis(4-methoxyphenyl)adamantane (TMPA) (6), which can further bereacted with BBr₃ to yield THPA (7). THPA can then be reacted in variousnucleophilic aromatic substitution reactions with activatedfluoroaromatics in the presence of potassium carbonate employingstandard procedures (e.g., Engineering Plastics—A Handbook ofPolyarylethers by R. J. Cotter, Gordon and Breach Publishers, ISBN2-88449-112-0) to produce the desired thermosetting monomers, or THPAmay be reacted with 4-halo-4′-fluorotolane (with halo=Br or I) in astandard aromatic substitution reaction (e.g., Engineering Plastics,supra) to yield tetrakis[4-(4-halophenylethynylphenoxy)phenyl]adamantane(8). In further alternative reactions, various alternative reactants mayalso be employed to generate the shaped thermosetting monomers.Similarly, the nucleophilic aromatic substitution reaction may also beutilized in a synthesis of a star shaped thermosetting monomer with asexiphenylene as the aromatic portion as depicted in FIG. 2D, in whichsexiphenylene is reacted with 4-fluorotolane to produce a star shapedthermosetting monomer. Alternatively, phloroglucinol may be reacted in astandard aromatic substitution reaction with1-(4-fluorophenylethynyl-4-phenylethynyl)-4-benzene to yield1,3,5-tris(phenylethynylphenylethynylphenoxy)benzene.

[0024] Where the cage compound is a silicon atom, an exemplary preferredsynthetic scheme is depicted in FIG. 3C, in whichbromo(phenylethynyl)aromatic arms (9) are converted into thecorresponding lithium(phenylethynyl)aromatic arms (10), which aresubsequently reacted with silicon tetrachloride to yield the desiredstar shaped thermosetting monomer with a silicon atom as a cagecompound.

[0025] Although it is preferred that the cage compound is an adamantaneor diamantane, in alternative aspects of the inventive subject matter,various cage compounds other than an adamantane or diamantane are alsocontemplated. It should be especially appreciated that the molecularsize and configuration of the cage compound in combination with theoverall length of the arms R₁-R₄ or R′₁-R′₆ will determine the size ofvoids in the final low dielectric constant polymer (by steric effect).Therefore, where relatively small cage compounds are desirable,substituted and derivatized adamantanes, diamantanes, and relativelysmall, bridged cyclic aliphatic and aromatic compounds (with typicallyless than 15 atoms) are contemplated. In contrast, in cases where largercage compounds are desirable, larger bridged cyclic aliphatic andaromatic compounds (with typically more than 15 atoms) and fullerenesare contemplated.

[0026] It should further be appreciated that contemplated cage compoundsneed not necessarily be limited to carbon atoms, but may also includeheteroatoms such as N, S, O, P, etc. Heteroatoms may advantageouslyintroduce non-tetragonal bond angle configurations, which may in turnenable covalent attachment of arms R₁-R₄ or R′₁-R′₆ at additional bondangles. With respect to substitutents and derivatizations ofcontemplated cage compounds, it should be recognized that manysubstituents and derivatizations are appropriate. For example, where thecage compounds are relatively hydrophobic, hydrophilic substituents maybe introduced to increase solubility in hydrophilic solvents, or viceversa. Alternatively, in cases where polarity is desired, polar sidegroups may be added to the cage compound. It is further contemplatedthat appropriate substituents may also include thermolabile groups,nucleophilic and electrophilic groups. It should also be appreciatedthat functional groups may be employed in the cage compound (e.g., tofacilitate crosslinking reactions, derivatization reactions, etc.) Wherethe cage compounds are derivatized, it is especially contemplated thatderivatizations include halogenation of the cage compound, and aparticularly preferred halogen is fluorine.

[0027] In further alternative aspects of the inventive subject matter,the cage compound may be re-placed by a non-carbon atom with apolygonal, more preferably tetragonal configuration. Contemplated atomsinclude a silicon atom, and particularly contemplated atoms includeatoms that exhibit polygonal ligand configuration and form covalentbonds with a resistance to oxidation greater than a carbon-carbon bond.Furthermore, alternative atoms may also include cationic and anionicspecies of a particular atom. For example, appropriate atoms are Ge, andP.

[0028] Where the thermosetting monomer has an aryl coupled to the armsR′₁-R′₆ as shown in Structure 2, it is preferred that the aryl comprisesa phenyl group, and it is even more preferred that the aryl is a phenylgroup or a sexiphenylene. In alternative aspects of the inventivesubject matter, it is contemplated that various aryl compounds otherthan a phenyl group or a sexiphenylene are also appropriate, includingsubstituted and unsubstituted bi- and polycyclic aromatic compounds.Substituted and unsubstituted bi- and polycyclic aromatic compounds areparticularly advantageous, where increased size of the thermosettingmonomer is preferred. For example, where it is desirable thatalternative aryls extend in one dimension more than in anotherdimension, naphthalene, phenanthrene, and anthracene are particularlycontemplated. In other cases, where it is desirable that alternativearyls extend symmetrically, polycyclic aryls such as a coronene arecontemplated. In especially preferred aspects, contemplated bi- andpolycyclic aryls have conjugated aromatic systems that may or may notinclude heteroatoms. With respect to substitutions and derivatizationsof contemplated aryls, the same considerations apply as for cagecompounds (vide supra).

[0029] With respect to the arms R₁-R₄ and R′₁-R′₆, it is preferred thatR₁-R₄ are individually selected from an aryl, a branched aryl, and anarylene ether, and R′₁-R′₆ are individually selected from an aryl, abranched aryl, and an arylene ether, and nothing. Particularlycontemplated aryls for R₁-R₄ and R′₁-R′₆ include aryls having a tolanyl,a phenylethynylphenylethynylphenyl, and a p-tolanylphenyl moiety, andtolanyl, phenylethynylphenylethynylphenyl, and p-tolanylphenyl moieties.Especially preferred branched aryls include a1,2-bis(phenylethynyl)phenyl, and particularly contemplated aryleneethers include p-tolanylphenyl ether.

[0030] In alternative aspects of the inventive subject matter,appropriate arms need not be limited to an aryl, a branched aryl, and anarylene ether, so long as alternative arms R₁-R₄ and R′₁-R′₆ comprise areactive group, and so long as the incorporation of the thermosettingmonomer comprises a reaction involving the reactive group. The term“reactive group” as used herein refers to any element or combinations ofelements having sufficient reactivity to be used in incorporating themonomer into a polymer. For example, contemplated arms may be relativelyshort with no more than six atoms, which may or may not be carbon atoms.Such short arms may be especially advantageous where the size of voidsincorporated into the final low dielectric constant polymer need to berelatively small. In contrast, where especially long arms are preferred,the arms may comprise a oligomer or polymer with 7-40, and more atoms.Furthermore, the length as well as the chemical composition of the armscovalently coupled to the contemplated thermosetting monomers may varywithin one monomer. For example, a cage compound may have two relativelyshort arms and two relatively long arms to promote dimensional growth ina particular direction during polymerization. In another example, a cagecompound may have two arms chemically distinct from another two arms topromote regioselective derivatization reactions.

[0031] It should further be appreciated that while it is preferred thatall of the arms in a thermosetting monomer have at least one reactivegroup, in alternative aspects less than all of the arms need to have areactive group. For example, a cage compound may have 4 arms, and only 3or two of the arms carry a reactive group. Alternatively, an aryl in athermosetting monomer may have three arms wherein only two or one armhas a reactive group. It is generally contemplated that the number ofreactive groups in each of the arms R₁-R₄ and R′₁-R′₆ may varyconsiderably, depending on the chemical nature of the arms and of thequalities of the desired end product. Moreover, reactive groups arecontemplated to be positioned in any part of the arm, including thebackbone, side chain or terminus of an arm. It should be especiallyappreciated that the number of reactive groups in the thermosettingmonomer may be employed as a tool to control the degree of crosslinking.For example, where a relatively low degree of crosslinking is desired,contemplated thermosetting monomers may have only one or two reactivegroups, which may or may not be located in one arm. On the other hand,where a relatively high degree of crosslinking is required, three ormore reactive groups may be included into the monomer. Preferredreactive groups include electrophilic and nucleophilic groups, morepreferably groups that may participate in a cyclo addition reaction anda particularly preferred reactive group is an ethynyl group.

[0032] In addition to reactive groups in the arms, other groups,including functional groups may also be included into the arms. Forexample, where addition of particular functionalities (e.g., athermolabile portion) after the incorporation of the thermosettingmonomer into a polymer is desirable, such functionalities may becovalently bound to the functional groups.

[0033] The thermosetting monomers can be incorporated into a polymer bya large variety of mechanisms, and the actual mechanism of incorporationpredominantly depends on the reactive group that participates in theincorporation. Therefore, contemplated mechanisms include nucleophilic,electrophilic and aromatic substitutions, additions, eliminations,radical polymerizations, and cyclo-additions, and a particularlypreferred incorporation is a cycloaddition that involves at least oneethynyl group located at least one of the arms. For example, in athermosetting monomer having arms selected from an aryl, a branched aryland an arylene ether, in which at least three of the aryl, the branchedaryl, and the arylene ether have a single triple bond, the incorporationof the monomer into the polymer may comprise a cycloaddition reaction(i.e. a chemical reaction) of at least three triple bonds. In anotherexample, in a thermosetting monomer wherein all of the aryl, thebranched aryl, and the arylene ether arms have a single triple bond, theincorporation of the monomer into the polymer may comprise acycloaddition (i.e. a chemical reaction) of all of the triple bonds. Inother examples, cycloadditions (e.g., a Diels-Alder reaction) may occurbetween an ethynyl group in at least one arm of the thermosettingmonomer and a diene group located in a polymer. It is furthercontemplated that the incorporation of the thermosetting monomers into apolymer takes place without participation of an additional molecule(e.g., a crosslinker), preferably as a cyclo addition reaction betweenreactive groups of thermosetting monomers. However, in alternativeaspects of the inventive subject matter, crosslinkers may be employed tocovalently couple a thermosetting monomer to a polymer. Such covalentcoupling may thereby either occur between a reactive group and a polymeror a functional group and a polymer.

[0034] Depending on the mechanism of incorporation of the thermosettingmonomer into the polymer, reaction conditions may vary considerably. Forexample, where a monomer is incorporated by a cycloaddition employing atriple bond of at least one of the arm, heating of the thermosettingmonomer to approximately 250° C. for about 45 min is generallysufficient. In contrast, where the monomer is incorporated into apolymer by a radical reaction, room temperature and addition of aradical starter may be appropriate. A preferred incorporation is setforth in the examples.

[0035] With respect to the position of incorporation of thethermosetting monomer into polymer it is contemplated that thermosettingmonomers may be incorporated into the backbone, a terminus or a sidechain of the polymer. As used herein, the term “backbone” refers to acontiguous chain of atoms or moieties forming a polymeric strand thatare covalently bound such that removal of any of the atoms or moietywould result in interruption of the chain.

[0036] Contemplated polymers include a large variety of polymer typessuch as polyimides, polystyrenes, polyamides, etc. However, it isespecially contemplated that the polymer comprises a polyaryl, morepreferably a poly(arylene ether). In an even more preferred aspect, thepolymer is fabricated at least in part from the thermosetting monomer,and it is particularly contemplated that the polymer is entirelyfabricated from the thermosetting monomer.

[0037] It should be especially appreciated that (1) the size of the cagecompound or the aryl, and (2) the overall length of the arms R₁-R₄ andR′₁-R′₆ that are covalently coupled to the cage compound will determinethe nanoporosity imparted by a steric effect. Therefore, where athermosetting monomer with a cage compound or a silicon atom is part ofa low dielectric constant polymer, and wherein the arms R₁-R₄ have atotal length L and the low dielectric constant polymer has a dielectricconstant K, the dielectric constant K will decrease when L increases.Likewise, where a thermosetting monomer with an aryl is part of a lowdielectric constant polymer, and wherein the arms R′₁-R′₆ have a totallength L and the low dielectric constant polymer has a dielectricconstant K, the dielectric constant K will decrease when L increases.Consequently, the size of the cage compound, the aryl, and particularlythe size of the arms in a thermosetting monomer can be employed to finetune or regulate the dielectric constant of a low dielectric constantpolymer harboring the thermosetting monomer. It is especiallycontemplated that by extension of the arms in a thermosetting monomerthe dielectric constant may be reduced in an amount of up to 0.2,preferably of up to 0.3, more preferably of up to 0.4 and mostpreferably of up to 0.5 dielectric constant units.

[0038] In an especially contemplated arm extension strategy depicted inFIG. 4, in which AD represents an admantane or diamantane group.Phenylacetylene is a starting molecule that is reacted (A1) with TBA(supra) to yield tetrakis(mono-tolanyl)-adamantane. Alternatively,phenylacetylene can be converted (B1) to tolanylbromide that issubsequently reacted (C1) with trimethylsilylacetylene to formtolanylacetylene. TBA can then be reacted (A2) with tolanylacetylene totetrakis(bis-tolanyl)-adamantane. In a further extension reaction,tolanylacetylene is reacted (B2) with 1-bromo-4-iodobenzene tobistolanylbromide that is further converted (C2) to bistolanylacetylene.The so formed bistolanylacetylene may then be reacted (A3) with TBA toyield tetrakis(tristolanyl)-adamantane.

[0039] It is particularly contemplated that the thermosetting monomersaccording to the inventive subject matter may be employed in adielectric layer of an electronic device, wherein preferred dielectriclayers have a dielectric constant of less than 3, and preferred electricdevices include an integrated circuit. Therefore, a contemplatedelectrical device may include a dielectric layer, wherein the dielectriclayer comprises a polymer fabricated from a thermosetting monomer havingthe structures

[0040] wherein Y is selected from a cage compound and a silicon atom, Aris preferably an aryl, R₁-R₄ are independently selected from an aryl, abranched aryl, and an arylene ether, R′₁-R′₆ are independently selectedfrom an aryl, a branched aryl, and an arylene ether and nothing, andwherein at least one of the aryl, the branched aryl, and the aryleneether has a triple bond.

EXAMPLES

[0041] The following examples describe exemplary syntheses ofthermosetting molecules according to the inventive subject matter, andpreparation of a low dielectric constant film.

Example 1

[0042]

[0043] Adamantane is brominated to TBA following a procedure aspreviously described in J. Org. Chem. 45, 5405-5408 (1980), by Sollot,G. P. and Gilbert, E. E.

[0044] TBA was reacted with bromobenzene to yieldtetrakis(3/4-bromophenyl)adamantane (TBPA) as described inMacromolecules, 27, 7015-7022 (1990) by Reichert, V. R. and Mathias L.J. The reaction resulted in the formation of various byproducts. HPLC-MSanalysis showed that the yield of the desired TBPA was approximately50%, accompanied by 40% of the tribrominated tetraphenyl adamantane andabout 10% of the dibrominated tetraphenyladamantane. Unexpectedly,however, when the product mixture was subjected to fresh reagent andcatalyst (bromobenzene and AlCl₃, 1 min at 20° C.), TBPA was obtained inyields of approximately 90%.

[0045] TBPA was reacted with phenylacetylene to yield the final producttetrakis(tolanyl)adamantane following a general reaction protocol for apalladium-catalyzed Heck ethynylation.

Example 2

[0046]

[0047] In a 500-mL 3-neck round-bottom flask, equipped with an additionfunnel and a nitrogen gas inlet, 4-iodobromobenzene (25.01 g, 88.37mmoL), triethylamine (300 mL), bis(triphenylphosphine)-paladium[II]chloride (0.82 g) and copper[I] iodide (0.54 g) were added. Then, asolution of phenyl-acetylene (9.025 g, 88.37 mmoL) in triethylamine (50mL) was added slowly, and the temperature of the solution was kept under35C under stirring. The mixture was stirred for another 4 hours afteraddition was completed. The solvent was evaporated on the rotaryevaporator and the residue was added to 200 mL of water. The product wasextracted with dichloromethane (2×150 mL). The organic layers werecombined and the solvents were removed by rotary evaporator. The residuewas washed with 80 mL hexanes and filtered. TLC and HPLC showed a pureproduct (yield, 19.5 g, 86%). Additional purification was performed byshort silica column chromatography (Eluent is 1:2 mixture of toluene andhexanes). A white crystalline solid was obtained after solvent removal.The purity of the product was characterized by GC/MS in acetonesolution, and further characterized by proton NMR.

[0048] The synthesis of p-ethynyltolane from p-bromotolane was performedin two steps. In the first step, p-bromotolane wastrimethylsilylethynylated, and in the second step, the reaction productof the first step was converted to the final endproduct.

[0049] Step 1 (Trimethylsilylethynylation of 4-bromotolane):4-Bromotolane (10.285 g, 40.0 mMol), ethynyltrimethylsilane (5.894 g,60.0 mMol), 0.505 g (0.73 mMol) ofdichlorobis(triphenylphosphine)-palladium[II] catalyst, 40 mL ofanhydrous triethylamine, 0.214 g (1.12 mMol) of copper[I] iodide, and0.378 g (1.44 mMol) of triphenylphosphine were placed into the N₂purged, 5-Liter 4-neck round-bottom flask, equipped with an overheadmechanical stirrer, condenser, and positioned inside a heating mantle.The mixture was heated to a gentle reflux (about 88° C.) and maintainedat reflux for 1.5 hours. The reaction mixture became a thick black pasteand was cooled. Thin-layer chromatographic analysis indicated completeconversion of starting material 4-bromtolane to a single product. Thesolids were filtered and washed with 50 mL of triethylamine, mixed with400 mL of water and stirred for 30 minutes. The solids was filtered andwashed with 40 mL of methanol. The crude solid was recrystallized from500 mL of methanol. On standing, lustrous silver colored crystalssettled out. They were isolated by filtration and washed with 2×50 mL ofmethanol. 4.662 g was recovered (42.5% yield).

[0050] Step 2 (Conversion of 4-(Trimethylsilyl)ethynyltolane to4-Ethynyltolane): To a 1-Liter 3 neck round-bottom flask equipped with anitrogen inlet, an overhead mechanical stirrer, was charged 800 mL ofanhydrous methanol, 12.68 g (46.2 mMol) of4-(trimethylsilyl)ethynyltolane, and 1.12 g of anhydrous potassiumcarbonate. The mixture was heated to 50° C. Stirring continued until nostarting material is detected by HPLC analysis (about 3 hours). Thereaction mixture was cooled. The crude solids were stirred in 40 mL ofdichloromethane for 30 min and filtered. The filtered suspended solidsby HPLC showed mainly impurities. The dichloromethane filtrate was driedand evaporated to yield 8.75 g of a solid. On further drying in an oven,the final weight was 8.67 g, which represented a yield of 92.8%.

[0051] TBPA (supra) was reacted with 4-ethynyltolane to yield the finalproduct tetrakis(bis-tolanyl)adamantane (TBTA) following a generalprotocol for a palladium-catalyzed Heck ethynylation reaction.

[0052] The so prepared TBTA was dissolved in cyclohexanone to obtain a10% (by weight) solution, 5 ml of which were spun onto two siliconwafers using standard procedures well known in the art. The TBTA waspolymerized on the wafer by heating to a temperature of about 300° C.,and cured at a temperature of 400° C. for 1 hour. The k-value wasdetermined to be 2.57. It should be especially appreciated that when thek-value was compared to the k-value of TTA, (which is a structuralanalog to TBTA with a shortened length of the arms) the k-value of TTAwas higher at about 2.60. Thus, the contemplated decrease in the k-valuedue to an increased length of the arms extending from the cage compoundhas been experimentally confirmed.

[0053] Thus, specific embodiments and applications of compositions andmethods to produce a low dielectric constant polymer have beendisclosed. It should be apparent, however, to those skilled in the artthat many more modifications besides those already described arepossible without departing from the inventive concepts herein. Theinventive subject matter, therefore, is not to be restricted except inthe spirit of the appended claims. Moreover, in interpreting both thespecification and the claims, all terms should be interpreted in thebroadest possible manner consistent with the context. In particular, theterms “comprises” and “comprising” should be interpreted as referring toelements, components, or steps in a non-exclusive manner, indicatingthat the referenced elements, components, or steps may be present, orutilized, or combined with other elements, components, or steps that arenot expressly referenced.

What is claimed is:
 1. A method of producing a low dielectric constantpolymer, comprising: providing a thermosetting monomer having thestructure

wherein Y is selected from a cage compound and a silicon atom, and R₁,R₂, R₃, and R₄ are independently selected from an aryl, a branched aryl,and an arylene ether, and wherein at least one of the aryl, the branchedaryl, and the arylene ether has a triple bond; and incorporating thethermosetting monomer into a polymer thereby forming the low dielectricconstant polymer, wherein the incorporation into the polymer comprises achemical reaction of the triple bond.
 2. The method of claim 1 wherein Yis selected from the group consisting of an adamantane, and adiamantane.
 3. The method of claim 1 wherein the aryl comprises a moietyselected from the group consisting of a tolanyl, aphenylethynylphenylethynylphenyl, and a p-tolanylphenyl.
 4. The methodof claim 1 wherein the branched aryl comprises a1,2-bis(phenylethynyl)phenyl.
 5. The method of claim 1 wherein thearylene ether comprises a p-tolanylphenyl ether.
 6. The method of claim1 wherein at least three of the aryl, the branched aryl, and the aryleneether have a triple bond, and wherein the incorporation into the polymercomprises a chemical reaction of the at least three triple bonds.
 7. Themethod of claim 1 wherein all of the aryl, the branched aryl, and thearylene ether have a triple bond, and wherein the incorporation into thepolymer comprises a chemical reaction of all of the triple bonds.
 8. Themethod of claim 1 wherein R₁, R₂, R₃ and R₄ have a total length L, andthe low dielectric constant polymer has a dielectric constant K, andwherein K decreases when L increases.
 9. The method of claim 1 whereinthe polymer comprises a poly(arylene ether).
 10. The method of claim 1wherein the step of incorporating the thermosetting monomer into thepolymer takes place without participation of an additional molecule. 11.A method of producing a low dielectric constant polymer, comprising:providing a thermosetting monomer having the structure

where Ar is an aryl, and R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆, areindependently selected from an aryl, a branched aryl, an arylene ether,and nothing, and wherein each of the aryl, the branched aryl, and thearylene ether have at least one triple bond; and incorporating thethermosetting monomer into a polymer thereby forming the low dielectricconstant polymer, wherein the incorporation into the polymer comprises achemical reaction of the at least one triple bond.
 12. The method ofclaim 11 wherein the aryl comprises a phenyl group.
 13. The method ofclaim 12 wherein Ar is selected from the group consisting of a phenylgroup and a sexiphenylene.
 14. The method of claim 11 wherein R′₁, R′₂,R′₃, R′₄, R′₅, and R′₆ have a total length L, and the low dielectricconstant polymer has a dielectric constant K, and wherein K decreaseswhen L increases.
 15. The method of claim 11 wherein the step ofincorporating the thermosetting monomer into the polymer takes placewithout participation of an additional molecule.
 16. The method of claim11 wherein the polymer comprises a poly(arylene ether).
 17. Athermosetting monomer having the structure

wherein Y is selected from a cage compound and a silicon atom, and R₁,R₂, R₃, and R₄ are independently selected from an aryl, a branched aryl,and an arylene ether, and wherein at least one of the aryl, the branchedaryl, and the arylene ether has a triple bond.
 18. A thermosettingmonomer having the structure

wherein Ar is an aryl, and R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆ areindependently selected from an aryl, a branched aryl, an arylene ether,and nothing, and wherein each of the aryl, the branched aryl, and thearylene ether have at least one triple bond.
 19. A thermosetting monomerhaving a structure according to formula TM-1:

wherein n=1-3.
 20. A thermosetting monomer having a structure accordingto formula TM-2:

wherein n=1-3.
 21. A thermosetting monomer having a structure accordingto formula TM-3:


22. An electrical device including a dielectric layer comprising apolymer fabricated from at least one thermosetting monomer from thegroup consisting of:

wherein Y is selected from a cage compound and a silicon atom, and R₁,R₂, R₃, and R₄ are independently selected from an aryl, a branched aryl,and an arylene ether, and wherein at least one of the aryl, the branchedaryl, and the arylene ether has a triple bond;

wherein Ar is an aryl, and R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆ areindependently selected from an aryl, a branched aryl, an arylene ether,and nothing, and wherein each of the aryl, the branched aryl, and thearylene ether have at least one triple bond;